Question: When did Franz Liszt begin his relationship with his partner Marie d'Agoult?
Paraphrase: When did Franz Liszt commenced his engagement with his partner Marie d'Agoult?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q41309 p:P451 ?s . ?s ps:P451 wd:Q253453 . ?s pq:P580 ?value}